1. Fields of the Invention
The present invention relates to a tacker, and more particularly, to a staple push unit of a power tacker.
2. Descriptions of Related Art
The conventional tacker known to the applicant is disclosed in FIG. 8, and comprises a motor 70 with an output shaft 72, and a cam 73 is connected to the output shaft 72. A staple push unit is located in the tacker and has a push plate 74, a switch plate 75 and a spring 77, wherein the spring 77 is located in casing 76, and the switch plate 75 is located beside the spring 77. The switch plate 75 is driven by the cam 73 so as to simultaneously activate the switch plate 75 and the spring 77. The push plate 74 is located above the switch plate 75. The user pulls the trigger 71 to activate the motor 70 and the output shaft 72 which rotates the cam 73. The cam 73 pushes the switch plate 75 and compress the spring 77 to store energy. As shown in FIG. 9, when the cam 73 rotates over the switch plate 75, the switch plate 75 is not pushed by the cam 73, so that the spring 77 is released and the energy of the spring 77 pushes the push plate 74 to eject the staple 78 out and into an object as shown in FIG. 10.
However, the cam 73 is cylindrical part with a smooth outside, and the spring 77 applies a significant force to the switch plate 75, so that the friction between the cam 73 and the switch plate 75 can easily wear out the both of the cam 73 and the switch plate 75. This may affects the precision of the ejection of the staples.
The present invention intends to provide a staples push unit of a power tacker to eliminate the shortcomings mentioned above.